1. Field of the Invention
This application is related to radio access networks involved in wireless telecommunications, and particularly relates to an internal interface (such as the Common Public Radio Interface (CPRI)) of a radio base station which links a radio equipment portion of the radio base station to a radio equipment control portion of the base station.
2. Related Art and Other Considerations
In a typical cellular radio system, wireless user equipment units (UEs) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network. Alternatively, the wireless user equipment units can be fixed wireless devices, e.g., fixed cellular devices/terminals which are part of a wireless local loop or the like.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a radio base station. A cell is a geographical area where radio coverage is provided by the radio equipment at a base station site. Each cell is identified by a unique identity, which is broadcast in the cell. The radio base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a control node known as a base station controller (BSC) or radio network controller (RNC). The control node supervises and coordinates various activities of the plural radio base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UMTS is a third generation system which, at least in some respects, builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a radio access network providing wideband code division multiple access (WCDMA) to user equipment units (UEs).
In many radio access networks the radio base station is a concentrated node with essentially most of the components being located at concentrated site. In the future mobile network operators may be afforded more flexibility if the radio base station is configured with a more distributed architecture. For example, a distributed radio base station can take the form of one or more radio equipment portions that are linked to a radio equipment control portion over a radio base station internal interface.
One example of an internal interface of a radio base station which links a radio equipment portion of the radio base station to a radio equipment control portion of the base station is the Common Public Radio Interface (CPRI). The Common Public Radio Interface (CPRI) is described in Common Public Radio Interface Specification Version 1.0 (Sep. 26, 2003) and Version 1.1 (May 10, 2004), and which are incorporated by reference herein in their entirety.
As illustrated in FIG. 13, the radio equipment control portion can take the form of a radio equipment controller (REC) 1322 which is located at a main site 1323. The radio equipment portion, such as radio equipment (RE) 1324, is typically situated at a remote site 1325. There may also be various other structures or units located at either the main site or the remote site which comprise, interface, or communicate with the radio base station. For example, FIG. 13 shows a horizontal pole or mast 1300 at the remote site 1325 which supports and holds aloft at least one or more antenna 1302. At the remote site also are one or more tower mounted amplifiers (TMA) 1304 which are connected between antenna 1302 and radio equipment (RE) 1324. The antenna 1302 may be a remote electrical tilt (RET) antenna, i.e., an antenna whose tilt can be controlled by radio equipment controller (REC) 1322 for controlling the coverage area. In addition, some radio base stations are in communication with other nodes of the radio access network (RAN) over radio based transmission links via one or more Transmission network units 1306. The Transmission network unit(s) 1306 serve, e.g., to receive the radio transmissions from other RAN nodes and to forward the transmissions over traditional transmission lines (e.g., E1/T1 or STM1) to the radio base station.
As shown in FIG. 13, a cable for the internal interface 1326 which connects the radio equipment controller (REC) 1322 and the radio equipment (RE) 1324 is conventionally only one of the cables extending between main site 1323 and remote site 1325. Additionally there are other cables, such as (for example) a transmission cable 1310 which extends between radio equipment controller (REC) 1322 and the Transmission network unit 1306 for the above-mentioned purpose of forwarding the transmissions over traditional transmission lines (e.g., E1/T1 or STM1) to the radio base station. In FIG. 13, the N number of E1s refers to the transmission need of the radio base station, which is typically two to eight E1s.
One or more antenna control cables 1312 may also extend between the main site 1323 and remote site 1325. Each antenna control cable 1312 has a proximal end connected to radio equipment controller (REC) 1322, and distal connections at remote site 1325. For example, the antenna control cable 1312 can be connected to distinct remote units in the form of the tower mounted amplifiers (TMA) 1304. If the antenna 1302 is a remote electrical tilt (RET) antenna, the antenna control cable 1312 can also be connected to a RET unit or other suitable controls of antenna 1302. Often each antenna unit has its own antenna control cable (e.g., a six antenna radio base station may typically have six antenna control cables). Sometimes the TMA and RET share cables.
As illustrated in FIG. 13, there are several cables extending from radio equipment controller (REC) 1322 to the remote site 1325 and up the mast 1300. The radio equipment (RE) 1324 itself may be mounted on mast 1300 as shown in FIG. 13. Each of the cables requires separate monitoring and maintenance, and each is subject to environmental or external influences and circumstances.
What is needed therefore, and an object of the present invention, is a technique for consolidating transmissions between a radio equipment controller (REC) and a radio equipment (RE) 24 of a distributed radio base station.